The invention relates to an image recording sensor which comprises a preselected line-shaped pattern of photodetectors for recording an image, the photodetectors being coupled to an image processing circuit. Such one or two-dimensional photodetector arrays are, for example, integrated circuits of charge-coupled memories.
These image recording sensors find application in image generation, image reproduction or image processing, for object recognition, and/or object tracking as well as for target recognition. For object recognition and/or object tracking, the image recording sensor is succeeded by an image processing circuit, in order to recognize a selected object on the basis of its form in the image.
In target recognition, the target to be recognized is in many cases, for example, a light-tagged missile unambiguously emphasized by its intensity against all other image elements.
In known image recording sensors, the discrete photodetectors corresponding to the pixels (picture elements) of the sensor are read sequentially and then digitally processed in order to carry out an object position determination or a target recognition.
In the addressed problem of target recognition, as a rule, the total image recorded by the image recording sensor is not of interest. Rather, what is essential for target recognition are only the coordinates of the picture element associated with the target. The process applied until now, i.e., to read the total image from the image recording sensor and allow it to be processed by an image processing circuit in order to find these coordinates, is, therefore, cumbersome and slow. A more rapid target recognition and target tracking is in many cases, desirable.
The invention is based on the task of providing an image recording sensor of the kind under discussion, with which significantly faster and more economical operation is achieved and wherein objects and/or targets can be recognized and their picture element coordinates unmistakably given.
Pursuant to the invention, an image recording sensor comprises a preselected line-shaped pattern of photodetectors for recording an image. The photodetectors are coupled to an image processing circuit wherein at least one part of the image processing circuit is integrated in the image recording sensor. To this end, the image recording sensor comprises a plurality of discrete cells, each of which is assigned to a predetermined one of the photodetectors. The cells are each coupled via column and row lines to encoder/decoder circuits for generating address information for a particular cell under certain conditions, as will appear. Moreover, each cell includes a capacitor to store the photocharge of the complementary photodetector and a voltage comparator to compare the capacitor voltage with a preselected reference comparison voltage. The comparator is coupled to an output circuit operable to transmit a signal to the column and row lines when the capacitor voltage is greater than the reference voltage, as determined by the voltage comparator, such that the encoder/decoder circuits generate the address information only when the charge of the photodetector of a particular cell is greater than the predetermined reference voltage.
Accordingly, the image recording sensor according to the invention is built in the states integrated form so that after each measuring cycle only the coordinates of the picture elements that are of interest are supplied directly, whereupon the image recording sensor begins the next measuring cycle. Instead of, as in known image recording sensors, after an image integration period to read out the data of all pixels and then to carry out the object position location with digital image processing methods, the sensor supplies, for such case, a single data word, namely the image element coordinates of the searched objects and can subsequently immediately begin with the next photocharge integration phase. In this procedure, a maximum amount of data reduction is achieved.
In the invention, one-and two-dimensional image recording sensors operating associatively are created, which do not supply intensity values per picture element, but only the addresses of the picture elements that are of interest, i.e., in which the intensity value of the photocharge exceeds a given level. With such image recording sensors having integrated image processing, it is possible to determine directly the picture element speed and the direction of the picture element velocity for one or the lightest picture elements of interest.
The image recording sensor according to the invention is very fast reacting; the reaction speed corresponds in the extreme case to that of discrete detectors. In addition, with the image recording sensor according to the invention, the reaction speed can be adapted to the particular object luminosity.
The image recording sensor according to the invention is produced in accordance with integrated circuit technology. In this manner, the input control circuit and the output circuit can be produced with field effect transistors and gates, in particular with field effect transistors and gates with a multi-gate transistor.
The invention is explained in greater detail with reference to embodiments in conjunction with the drawing, in which: